Treatment of printing felts



March 28, 1944. J w 1055 ET AL 2,345,179

TREATMENT OF PRINTING FELTS Filed April 10, 1942 POROUS ZONE lMPERV/OUSZONE,

Patented Mar. 28, 1944 TREATMENT or PRINTING FELTS John W. Close,Lombard, and Clifford H. Hoot,

Chicago, Ill., assignors to United Wall Paper Factories, Inc., a.corporation of Delaware Application April 10, 1942, Serial No. 438,362

1 Claim.

The invention relates to the treatment of printing felts and is ofparticular value in connection with a type of felt (meaning a continuousbelt of flexible porous fabric) which is employed in the printingindustry for the purpose of transferring liquid ink or color from asupply source to a printing surface, for example a plate or roll.

The invention is of particular value in connection with the manufactureof wall paper which is generally printed upon a machine which embodies acentral platen roll having a plurality of printing stations (sometimesas many as twelve for twelve different colors) around its circumference.Each of these printing stations usually involves a pattern roll which isof the relief type, the relief areas which actually do the printingserving to apply the color to the paper web which is trained around thecentral platen roll of the machine. With such an arrangement, the coloror ink is applied to the relief or printing areas of the pattern roll bymeans of a porousbelt or felt trained around a set of rollers, usuallyfour in number, which belt receives its ink or color from a suitable inkor color supply.

It has been found that when using the ordinary color transfer belt,generally made of a high quality of wool fabric, that portion of thebelt which registers with the printing zone of the pattern rollerremains substantially intact and fully efficient for a very long periodof time, while the ends or margins of the belt which extend beyond theprinting zone deteriorate with relative rapidity, making it necessary toreplace the belt frequently, at great expense.

One of the principal difliculties encountered has been the cracking orbreaking of the edges of the belt, apparently due to loss of flexibilityof the fabric in these marginal zones. We have discovered that thisstiffening and consequent cracking of the belt fabric in the marginalzones is due to the fact that, when the belt receives its supply of inkor color from the fountain or other source, the entire width of the beltbecomes impregnated with the ink or color and, while the ink in theprinting zone of the belt is used up and being constantly replenishedwith a new supply, the ink in the marginal or non-printing zones of thebelt remains in the fabric or structure of the belt in a relativelyundisturbed condition over an extended period of time. Apparently, underthese conditions, the solid or pigment constituents of the ink or colorbecome concentrated in the fabric of the belt and possibly form a moreor less cement-like deposit which materially reduces the flexibility ofthe fabric in these unused marginal zones and so causes the earlybreak-down before referred to.

Hence, it will be seen that the primary object of the present inventionis to provide, in a belt of the character referred to, some method ormeans by which the flexibility and elasticity of the unusued marginalportions of the felt will be preserved. Further objects are to providean improved arrangement of the class referred to which does not requireany material change, and in most cases no change whatsoever, in thegeneral arrangement of the equipment.

These objects are attained by treating the unused marginal portions ofthe belt in such a manner that the particles of pigment will notaccumulate in the interstices of the fabric, and, to effect this result,these marginal zones of the belt, or at any rate their porous outersurface layers, are charged with a solution or dispersion which, upondrying, leaves the pores of the belt sub stantially filled with aflexible elastic material such as rubber or latex; This material, whilenot materially interfering with the flexibility of the fabric, serveseffectively to bar the entrance of particles of pigment or otherunwanted material into the interstices of the fabric.

The drawing accompanying this application illustrates in somewhatdiagrammatic form a specific application of the invention to a singlestation of a wall paper printingpress. In the draw- Fig. 1 represents indiagrammatic form an elevation of the equipment;

Fig. 2 is a section taken on the line 2-2 of Fig. 1; and

Fig. 3 is an enlarged 3--3 of Fig. 1.

In'the drawing, it will be seen that the paper web H1 is supported on aplaten which takes the form of a cylinder Ii, positively driven by meansnot shown. It will be understood that the pattern roll 12 is alsopositively driven and rotates at such speed that the circumferencetravels at the same linear speed as the circumference of the platencylinder l l In the multi-color printing press a portion of which isherein illustrated, the printing area is in relief as shown at I3, itbeing understood that these relief areas or elevations I3 are the onlyportions of the roller l2 which make contact with the paper [0, and, ofcourse, these relief areas are of the proper shape or configuration andsize to produce upon the paper an impression in that particular color atthe places desired in the complete wall paper pattern.

section taken on the line The relief areas in the printing zone of thepattern roller l2 receive their supply of ink and color from a belt [4which, except as otherwise described, is the usual endless wool fabricbelt of such lateral width that the ends of marginal zones projectbeyond the ends of the printing zone of the pattern roller l2, as shownbest in Figs. 2 and 3, and preferably overhang slightly the ends of thecylindrical portions of the belt rollers l5, l6, l1 and I8, as shownbest in Fig. 2. In accordance with the usual practice, the belt rollerI6 is driven so as to effect the necessary movement of the belt past,and in contact with, the pattern roll l2. However, it need notnecessarily be particularly well synchronized with the drive for thepattern roll l2 and platen cylinder II. The lower roll 18 serves as theupper roll of a pair which also include the color pick-up roll I 9dipping into a trough 20 containing a supply of suitable liquid color2|. As is usual in modern wall paper manufacture, the ink or color 2i isof the water dispersion type. It will be understood that, as the belttravels in the nip of th two rolls I8 and I9, it will receive color fromthe circumference of the roll l9, which amount of color picked up by thebelt is, to a certain extent, determined by the relative pressurebetween the rolls [8 and I9. Ordinarily, it will be found advisable topick up an excess of color which may be doctored off the front orcontact surface of the belt H by means of any suitable doctoringarrangement indicated at 22.

The arrangement so far described is such as is understood to have beencommon practice in this art for a long time.

In printing press arrangements of the character described, the belts areusually about two or three inches wider than the face length of thepattern roll. For example a pattern roll having a printing face 22inches to 24 inches long can usually be served with a belt which is 2.4inches to 28 inches wide, so that there will be at each margin of thebelt an unused or non-printing portion from 1 to 2 inches in width. Thisis the part of the belt that gives the trouble according to theheretofore existing practice.

To overcome this difliculty, before a new belt is installed in theequipment, we measure off the length of face of the printing zone of thepattern roller and compare that length with the total width of the belt,and thus determine how wide the unused marginal zones of the belt willbe under the particular conditions. The new belt is then rolled up intoa fairly compact coil and one end of the .coil or roll, holding the axisof the coil vertical, is lowered into a suitable fiatbottomed receptaclewhich contains a suflicient depth of the proper impregnating material tosoak the unused marginal portion of the belt.

After one edge of the belt has been impregnated in this manner, the coilis reversed and the opposite edge of the belt is similarly treated.

After both edges of the belt have been impregnated in this manner, thebelt is unwound or stretched out, and the impregnated marginal zones areallowed to dry.

Preferably, the impregnating liquid consists of a commercial type oflatex dispersion in Water, containing about 36% rubber, and anaccelerator and a vulcanizer of the cold type.

Using a latex dispersion of the type described, it is found that thematerial will penetrate the belt fabric for a distance equal to aboutonequarter of the thickness of the belt, so that, when the margins ofthe belt are treated in the foregoing manner, there will be a relativelyuntreated central layer representing about one-half of the wholethickness of the belt. According to our practice, we have not found itnecessary to impregnate this central layer or core of the belt.

In certain cases, it may prove to be advisable to treat the entirenon-working or inside face of the belt with the same type of solution,using a brush or roller applicator. In this case, sufficient material isapplied to penetrate into the face of the belt for a distance equal toabout onequarter of its thickness. This is of advantage sometimes whenthe belt is used to apply colors containing certain red pigments ormicaceous materials. Furthermore, this treatment of the non-- workingface of the belt is of some value in preventing the loss or waste ofcolor caused by the ink passing completely through the belt andnaturally simplifies the clean-up problem.

Whereas the old type of untreated belt usually is found to break downafter having been used for printing about 300,000 twenty-four foot rollsof wall paper, precisely the same type of belt, when subjected to ourimproved preliminary treatment, is still efiective after having beenused for the printing of more than 1,000,000 of such rolls of wallpaper.

The invention is capable of certain modifications which will be apparentto those skilled in the art, and the scope of the invention should bedetermined by reference to the appended claim.

We claim:

An endless wool fabric or felt belt for feeding to a wallpaper printingroller surfacing fluid comprising a Water-dispersion of insolubilizablingredients, said belt having the border surface layers thereofoutwardly of the area of engagement of said belt and roller treated witha rubber-like, water-resistant material so as to immunize said bordersurface layers against impregnation by said surfacing fluid.

JOHN W. CLOSE. CLIFFORD H. HOOT.

